Many types of self-propelled agricultural harvesting machines include a chassis that is equipped with driven front wheels and steerable rear wheels. Examples of these types include combines and forage harvesters. A front harvesting attachment is attached to the front side of the chassis of the harvesting machine for taking up the harvested crop lying or standing on a field, that delivers the harvested crop during the harvesting operation to an intake conveyor connected to the chassis, that is designated in combines as a slope conveyor and in forage harvesters as intake housing. The intake conveyor brings the harvested crop into the interior of the chassis in which harvested crop processing arrangements are arranged, these include threshing, separating and cleaning arrangements in combines and chopper assemblies in forage harvesters.
In many cases the front harvesting attachments are removable, but are otherwise rigidly attached to the intake conveyor. In order to conform to the contour of the ground the intake conveyor is usually fastened, free to pivot about an axis extending horizontally and transverse to the forward operating direction with respect to the chassis of the harvesting machine, by means of an actuator. An appropriate control arrangement detects the height of the front harvesting attachment above the ground by means of a sensor and controls the actuator in such a way that a desired height or a desired contact pressure of the front harvesting attachment on the ground is attained. In addition, the control arrangement can pivot the front harvesting attachment about an axis extending horizontally and in the forward operating direction of the harvesting machine relative to the intake conveyor (EP 1 269 823 A), which is useful, for example, with slope combines with automatic horizontal orientation of the chassis with wheels, adjustable in their height, in an operation on a side slope. It has also been proposed that the front harvesting attachment be pivoted automatically about an axis extending horizontally and transverse to the direction of operation relative to the intake conveyor (DE 295 119 842 U) in order to attain an optimum cutting angle of the mowing knives relative to the harvested crop at all times. Accordingly front harvesting attachments that can be pivoted about horizontal axes relative to the intake conveyor are fundamentally known.
Since in the state of the art the front harvesting attachments cannot be moved about the vertical axis relative to the intake conveyor or the chassis of the harvesting machine, they follows the movement in the steering direction of the steered rear wheels of the harvesting machine together with the chassis. With larger operating widths of the front harvesting attachment the outer ends of the front harvesting attachment are very far from the center between the front wheels of the harvesting machine, not only in the transverse direction but also in the forward direction. This distance results in a very large possible radius of the outer end of the front harvesting attachment, so that it is relatively difficult to maneuver the harvesting machine during the free cutting of the radius ahead of the turn in the headlands of the field. In order to free cut the corners it may become necessary under certain circumstances, to perform several forward and reverse passes of the harvesting machine, these are accompanied by a great loss of time.
Moreover, harvesting machines with center pivot steering are known (U.S. Pat. No. 4,663,921 A, DE 103 26 367 A), that are provided with a chassis divided into two halves with a front half and a rear half that are fastened to each other so as to pivot about a vertical axis. Each of the halves is provided with wheels attached rigidly on each side, that is, the wheels cannot be steered. The movement of the halves about the vertical axis produced by means of a steering cylinder defines the direction of operation of the harvesting machine. The front half of the chassis carries a front harvesting attachment. Due to the center pivot steering the imaginary axis of rotation, about which the front harvesting attachment rotates when steered, is offset somewhat towards the front compared to harvesting machines with one-piece chassis, however, this difference is not clearly noticeable with respect to the possible outer radius at the end of the front harvesting attachment. In addition, a rather high cost is entailed when harvested crop is to be transported from the front half of the chassis to the rear half of the chassis.
For mowing vehicles with several mowing units arranged side by side alongside each other it has been proposed (FR 2 427 774 A, DE 196 20 070 A) that the center mowing unit, that is attached to the front side of the mowing vehicle, be shifted to the side depending on the immediate steering angle of the mowing vehicle, or pivoted about the vertical axis, in order to cover to the side of the strips mowed by the individual mowing units, even during operation around a curve. With such mowing vehicles the harvested crop is not brought into the interior of the mowing vehicle.
JP 2004 201 580 A describes a combine in which the cutter head can be pivoted to the side about the vertical axis in order to provide a better access to the front side of the combine for maintenance purposes.
The purpose of the invention is seen in the need to provide a self-propelled harvesting machine with steerable rear wheels or other propulsion devices, that can be maneuvered on a field without any problems.